class_docstr: A node in an OverlayGraph. Corresponds to a TensorFlow Tensor.
    
code: def __init__(self, name, overlay_graph):
      self.name = name
      self.overlay_graph = overlay_graph
      self.tf_graph = overlay_graph.tf_graph
      try:
          self.tf_node = self.tf_graph.get_tensor_by_name(name)
      except:
          self.tf_node = None
      self.sub_structure = None
  
imports: from collections import defaultdict
  import numpy
  import tensorflow
label_desc: Use image node_id 1 to create a new OverlayNode object  with example: obj = OverlayNode(name, overlay_graph)